1. Field of the Invention
The following description relates generally to an air circuit breaker, and more particularly to a withdraw-in and withdraw-out apparatus (herein after referred to as apparatus) for an air circuit breaker capable of preventing breakage of the apparatus that restrains withdraw-in and withdraw-out of a breaker body when an excessive force is applied by a user in the process of the breaker body being withdrawn in and withdrawn out from a cradle, and accurately checking the withdrawn-in and withdrawn-out states of the breaker body to thereby enhance convenience in the use of the product.
2. Background Art
Generally, an air circuit breaker is divided into a fixed type fixedly installed between a power source and a load, and a drawer type in which a breaker is movable so as to be separated from the power source and a load in order to facilitate maintenance and secure stability, according to accommodation and fixing method of a breaker body. The drawer type air circuit breaker is typically divided into a cradle, and a breaker body movable so as to be pushed in or pulled out from the cradle.
The fixed type air circuit breaker is so configured as to have an intrinsic terminal to be connected to an electrical power at a rear surface thereof, while the cradle-mounted drawer type air circuit breaker is disposed with a power source connection terminal connected to power source and a load connection terminal connected to electrical load equipment.
In other words, the drawer type air circuit breaker is such that the breaker body is translocated by a separate translocation apparatus disposed underneath the cradle to be connected to a terminal inside the cradle, and connected to a power source connection terminal connected to power source and a load connection terminal connected to electrical load equipment, where the draw type air circuit breaker may assume one of the three different situations:                1. “Connected (Service) Position” where power as well as control circuit is connected so that the breaker body is completely connected to a terminal inside the cradle.        2. “Test Position” where power circuit is disconnected but control circuit is connected. In this position, the circuit breaker can be tested for proper functioning without switching and/or carrying power.        3. “Disconnected (Isolated) Position” where the breaker body is also disconnected from the power source and external power system circuit.        
The withdraw in and withdraw out apparatus (hereinafter referred to as apparatus) disposed underneath the cradle for translocating the breaker body includes a moving rack for linearly translocating the breaker body disposed thereon, and a screw shaft spirally connected to the cam to convert a rotating force from a handle to a linear force. The apparatus may further include a lever and a screw rotatably connected via a coupling, and the coupling may rotatably include an indicator at one side thereof.
The lever is disposed at one side thereof with a hexagonal groove for rotating with the handle. The breaker is withdrawn in and out from the cradle in such a manner that the screw is rotated along with the rotation of the lever by the handle to linearly move a supporter fixedly mounted at the breaker body from a fixed block fixed at the cradle side.
There are shortcomings in the conventional air circuit breaker thus described in that a user cannot recognize a withdraw-in operation even if a breaker body is put into a connected position to thereby complete the withdraw-in operation of the breaker body, and if a lever is forcibly rotated, the apparatus may be destroyed to push the breaker body further into the cradle, which in turn may destroy other remaining constituent elements of the air circuit breaker.